Perpetual calendar



Jan. 25, 1944. J. Q. STEWART PERPETUAL CALENDAR Filed oct. 15, 19211 3 Sheets-Sheet 1 INVENToR Jay/v o. .srEwA/zr BY ATTORNEY v Jan. 25, 1944. 1 Q, STEWART 2,340,153

PERPETUAL CALENDAR Filed Oct. 15, 1941 3 Sheets-Sheet 3 ATTORNEY Patented Jan. 25, 1944 2,340,153Y Y .n

IERPE TUAL vCALI DAR John Q. stewart, Pr'icetonl N. J. Application October 15, 1941, .Serial No. ,414,989

(Cl. l0-1079 3 Claims.

The present invention relates generally to calendars and more particularly to improvements in perpetual calendars.

The principal object of my invention is to provide a calender which in itspattern of association of the days of the week with the days of a month presents the appearance .of an ordinary simple familiar calendar, whether showing ,a single month of the current year or a sequence yof months; and which, unlike the ordinary calendars in common use, does not expire at the end of a year or other period but, Without recoursetoV any data not a part o f the various scales of the apparatus itself, expeditiouslycan he set month after month, year after year, never becoming obsolete. y

Another object, implicit; in the accomplishment of the rst, is to provide a perpetual calendar similar in appearance to any ordinary calendar which readily can be set. for any month Ain vthe near or far past `or future, thus vdetermining the day of the week corresponding Vto any date, whether New Style or `Gregorian (our common reckoning), or Old Style or Julian. Although various numerical tables and mechanical devices already exist for finding the day of the Week corresponding to any date, the `method of operation of my device is of particular ease, Yand since the scales when set have the familiar appearance ofv an ordinary calendar this device vividly'presents to unskilled users the whole chronological environment of the required date.

A further object is to attain the objects already mentioned by means simple and cheap yet elegant and compact. That previous devices have not succeeded in this is indicated by their failure to displace from common use any appreciable number of the ordinary calendars, notwithstanding the drawback of early obsolescence which these do not include within their own scalesall Ithe data which ,the .user requires to 4set kthem .corrrectly. Mydevice is lparticularly advantageous in .its economy ,of space, .becausetheratio ,irarea of .the effective face .of the calendary..pronerfto thesupplementary scales is relativelyflarge. A

With `the aboveobjects in view, theinvention consists .oj'f `certain novel features, ,as hereinaft ,rE shown anddescribedand then specifically-pointed. out in the claims.

In the .accompanying drawings: V Figures la and lb taken ,together illustrate the invention .embodied ,in the form fof .a plurality..ofl year-cards and month cards; Y Figure 2 illustrates ,the manner lwhich one of the year-cardsshown in Figure 1b cooperates" with one of the month-'cards shownfinl-Figure '1c to'produce a familiar ,calendarpattelm n Figure 3 illustratesV va s amplemonth .cardof another embodiment wherein the current ,mo'iitfhli preceding y month and the while .the successioni'of calendardat'es-inv(living`- the century, the :yeaivin thecentury, the-monthi in the year, .and the .day of the vmenta-wis. given-l by .certain -arithmetical rules. With vevery -da'y of the year,-beginmngeveryyea with January aletter can be'associated, A, B, repeating for consecutive days in1cyclical order, so that January v8 is always A again; January!! is"A B and so Won. Only- ',ebruary 1129, .whenit occurs," hasno letter. 'Consequentlmin'a' non-leap-year all the Sundays have the same letter, and this letter is called the dominical letter or Sunday letter of the year. The day of the week corre- 4Sponding to any given date, whether Gregorian or Julian, can be computed by adding four integers, each no greater than seven, and taking the remainder, after the integral sevens have been removed from the said sum, to designate the day of the week: as 1 for Sunday, 2 for Monday '1 for Saturday.

I shall call four such integers the characteristic integers. One of them is a function of the century year, differing in old and new styles. Another is a. function of the year in the century. Another is a function of the month, but for January and February is changed by unity in leapyears from its ordinary values (unless, as is sometimes done, the leap-year difference is put on the characteristic integer for the year, this being then considered changed by unity during January and February of "a leap-year as compared with its value during the remainder of the same year).

The other integer is merely the day-number in Y the month, or this number after the integral sevens have been removed, as 3 for the 17th of the month. The dominical letter for a given year a corresponds to the sum of the characteristic integers for the century and the year in the century.

With this arithmetical situation it is clear that any mechanical method of designating the four characteristic integers and adding them-.as step by step by'a succession of sliders-will determine the day'of the week corresponding to a given date;

WhileV a variety ,of devices for the purpose have been described, Ysome ofl them many years ago, noneof them has all the advantages of compactness 4combined in my device with the elimination off-mental operations and the preservation in all settings of the exact form of the kordinary `cal endar. v

Referring particularly to'Figures'la. andj 1b of the drawings, it' will be noted that` a` calendar incorporatingthe features of my invention may beA made in the vform of'- aplurality of cards;"more' particularly, twenty-oneL cards, seven of' which,

|00=|06 inclusive; are lyear-cards 'which' will 'be referred to "herein" as "masks, and fourteen' lof which, |09;` |09','||0, lland lll-'|20 inclusive, are monthcards. The group of month-cards |09,

|-0"and` ill-'|20 inclusive lrepresent the/twelve months of vany year other thandeap years while theV group of cards |09', Y||||' and ||||20 in# clusive represent' in this particular embodiment, the-twelve months of any leap year.

Each of the month cards is provided with thirteen columns and six (December has seven) rows of Vday numbers, -the order of numbers, in-

cluding blanks, beingdiierent on each card,but4

third positions are numbered ,8 through ,20 re.

specti'viely and the Y fourth row positions are numbered 15 through 27 respectively. Thefth row positions, of the A first ten vcolumns are numbered 22 through` 31 respectively and the sixth row positions of the rst three columns are numbered 29,r 'and' 31 respectively.

vThe manner 'in which'the'bolumns of each'of the other month cards are marked is believed to be apparent from the drawings.

Each one of the year masks H10-|06 inclusive is provided with an opening |01 which is preferably rectangular in shape. The openings |01 are preferably of the same size in all the masks being indeed just large enough to expose all the rows of any successive seven of the thirteen columns or positions of day numbers marked on the month cards hereinbefore described.

The opening of each successive year card is staggered by the width of one column of the month cards; thus, opening |01 of year card |00 if the year card is placed properly over any one of the month cards will expose all of the rows of the first seven columns of day numbers; the opening |01 of year card |0| will expose the second, third, fourth, fth, sixth, seventh, and eighth columns; the opening |01 of year card |02 will expose the third through the ninth columns; the opening |01 of year card |03 will expose the fourth through the tenth columns; opening |01 of year card |04 will expose the fifth through the eleventh columns; opening |01 of year card |05 will expose the sixth through the twelfth columns; and, opening |01 of year card |05` will expose the seventh through the thirteenth columns. Each mask carries a scale |08 of days of the week in the normal order immediately adjacent one side of its opening |01. Each scale may comprise the rst letter of each day of the week; namely, S, M, T, W, T, F, S and the letters are arranged so that the first letter registers with the first exposed column of its year card, the second letter registers with the second exposed column and so on. Instead of single letter abbreviations, longer abbreviations or the full names of the days of the week may be used in similar registration with the exposed columns.

It is preferable to mark each month card with' the name of the month it represents and to arf range such marking so that the name of the month will be exposed through the opening of any one of the year masks. f

In order to simplify placing a year card on a month card in correct registration, it is preferable to make all of the cards of the same size. In this way when any year card is placed face up exactly over any one of the month cards seven columns of day numbers will be exposed through the year cardwindowv |01, said exposed seven columns.

being designated by the seven days of the week marked on the mask while the unwanted six col-v umns of day numbers are hidden.

. Each of the masks can be marked with theV years for which it represents the correct setting, in other words, the correct designations of days of the monthA as days of the week. Since the Gregorian calendar repeats identically every 400 years, 2000 A., D.Vhaving the same calendaras 1600 A.D., 2001 as 1601, etc., it suffices for the Gregorian calendar to indicate only a consecutive series of 40o years.

Below are shown the' years appropriate for each year'maskfrom 1600 A. D. t'o 2000 A.'D. inclusive in the Gregorian'system; The appropriate year markingsV for each year card lmay be printed on' Years appropriate for year [Leap yearsare underlined] 1 (A) Year mask 100.

YearmasklOl. 1853 (C) Y' i Year mask 192.

(D) f Year mask 103.

(E) Year mask 104.

(F) Year mask 105.

Year mask 105A `'From the above it will be noted that in the embodiment shown in Figures 1a and 1b, the whole arrangement reduces to a pack of specially constructed cards, therebeing fourteen month cards, and seven year cards, all of the same size if so desired. When the proper year card is placed exactly over the proper month card, the opening in the year card exposes the correct number of days for that month and year, in sequence, and having their correct designation asdays of the week-the visible effect being exactly that of the ordinary calendar.

The size of the resulting perpetual calendar ls not greatly increased as compared with an ordinary calendar having the same size printing or marking, and this is a special advantage of this embodiment.

Figure 2 shows the way the calendar appears when the year card or mask |03 which is good for the years noted in the fourth group of the above table is placed over the 'month card |113 which is good for the month vof January 4ola'll those years except leap years.

Itis believed that a detailed description of vthe second embodiment of the invention `shown in Figures 3, 4., and 5 is not necessary to an underfstanding thereof; it being only necessary to state that each one vof the seven year masks,`only one of which is shown at |2| in Figure 4, isprovided with three openings |22, |23, and |24 representing a month, the preceding month, and .the :succeeding month, respectively; and that each of the month cards |25 only one of which is shown in Figure 3, is provided with three day number charts |26, |21, and |28 representing the day numbers forone of the monthsk and the .day numbers for the preceding month and the succeeding month respectively. Obviously more than three months may beexposed if desired. Because of the overlaps from December through March there are four special month cardsfor leap-years, or sixteen month cards in allin the embodiment illustrated. In Figure 5 there isshown the appearanceiof acalendarsusing the type of year masks and monthcardszshown in Figures 3 and 4. The Vexact arrangement is, of course, not significant; in# stead of showing the current month in larger type, a series of consecutive months printed in the same sized type andimmediately adjacent each to each could be shown simultaneously through a large opening in a mask appropriate for the year. 1 It is to be understood that none of the embodiments of the invention described are confined to the system of chronological reckoning which provides only one characteristic integer 0r dominical letter for a leap year while providing special alternate characteristic integers for January and February in leap years. With equal mechanical ease the system of a special integer for the rst two months of a leap year and another for the remaining ten can be used, with January and February always appearing with the same in-'g teger. Suche, system permits reduction of the number of month scales from fourteen to twelvei but requires a double marking of the year cards as respects leap years.

The number of month scales can be further reduced-to seven-if certain month scales are marked with the names of additional months according tothe following scheme- Referring to Figure la, let the card for January (common years) be marked also October; let January (leap years) be marked also April and July; let February (common years) be marked also March and November; let February (leap years) be marked also August; let May be marked May only; June, June only; let September be marked also December; and omit thecards marked in Figure la, March, April, July, August, October, November, and December. This arrangement has, however, the disadvantage that day numbers 1-31 inclu,- sive are exposed for every month. l'

Of course, a reduction in the number of month cards-but not in the number of scales-can be made by the obvious expedient of printing scales on both sides of the cards. Furthermore, the mask appropriate for years of dominical letter A, if reversed, is suitable for the G years; maskvB reversed for F years; mask C reversed for E1 years-Which device of turning the masks upside down reduces the required number to four. Only one mask indeed. is absolutely essential, if it lbe usable in' seven diierent positions so as to make its'opening expose any required consecutive seve'n columns of day numbers on'` the month scales;

And again the role of the masks and the cards can be interchanged Without the loss ot all the advantages of my invention-the masks being marked in the appropriate order, respectively, with the combinations of months enumerated in the preceding paragraph, for example; and each card carrying a scale of vday numbers as already described marked not with a month or months but instead with the years for which it is appropriate in combination with the masks Vwith markings thus altered. Y

Furthermore, devices of this same general character could be used, with appropriate changes, for any calendar that might be devised at all along the lines of the present Gregorian calendar. Say one with seventeen months of Widely varying lengths and an .altered rule for leap years.

. It should be understood also that for Julian dates the years would fall into diferent sets, as compared with the Gregorian sets `already enumerated. The Julian sets of years likewise can be marked on the appropriate year masks, or indicated in a formula or table or correspondences.

The number of patterns of each of the month cards shown in Figure la can be altered together in the following manner withouty essential difference; strike out the right-hand or thirteenth column of day numbers, and'substitute at the extreme left a new -column of day numbers hav- :lng numbers less by unity than the present rst column of the respective month. For example, January (Figure la.) for common years when so altered becomes:

which thus agrees'in all respects with the card marked May in Figure 1a. This process can be repeated as many times as desired, provided all the month cards are -changed together, and provided the cooperating change is made in the markings of the year masks; i. e., with the pattern for January shown just above mask |00 (Figure la) must be lettered G instead of A, and the years of its appropriate use are changed to correspond; maskll must be lettered A instead of B; and so on, mask |06 being lettered` F instead of G.

' What I claim is: 1. In a perpetual calendar, a plurality of mem-v bers bearing scales of days of the month, each scale being appropriate for a particular month and comprising at least thirteen positions of day-numbers, a plurality of masking members cooperating with said scales each of,'said masking members being marked in a different position with a scale of days of the week and having-an aperture adjacent to said scale for exposing seven successive positions of saidday-numbers,-l the seven markings of each of said scales of days of the wee registering respectively with the exposed seven successive positions of day-numbers, said thirteen positions of day-numbers being so patterned that any seven successive positions inc lude all the day-numbers of the respective month and no other numbers and that successive daynumbers in a single column differ by seven: the relation to each other of the number-patterns for individual months being suchthatl if. any particular position in one scale be designated as Sunday, the next one in order Monday, and so on through Saturday, .then if Vthese same designations are applied to the corresponding positions in certain others ofthe plurality of scales, the indications which result of the days of the week of all the months so treated will be correct in years which have a certain dominical letter.

2. In a perpetual calendar, a series of seven equi-sized templates, one for each dominical letter, each marked at seven equally-spaced positions with the days of the week, in order Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, without repetition, said scale of days of the Week on each template being adjacent to a Window which is the same size on all the templates but differently placed in accordance with the dominical letter of the year for which the template is appropriate; and a series of at least 14 cards, each marked at thirteen equally-spaced positions or columns with a scale'of days of the month, the interval between successive positions being the same as between the positions of the days of the week on the templates: the size and positions on the template of the window being such that each template when placed in a standard manner above any card hides six of the thirteen columns of Aday-numbers and exposes seven consecutive columns thereof: the position of the window from template to template in the series being different by the constant interval between columns, so that each of the seven templates exposes a different combination of seven columns, but the same combination on every card, hiding all other columns on all the cards.

3. In a perpetual calendar, a series of seven substantially equi-sized templates, one for each dominical letter, a Window formed in each template, each template being marked adjacent its Window with days of the week indicia, in order Sunday, Monday, Tuesday, Wednesday, Thursday, Friday and Saturday without repetition, all of said Windows being of substantially the same size but diierently positioned on said templates in accordance with the dominical letter of the year for which the template is apropriate; and a series of fourteen cards, there being an individual card for each of the months of March, April, May, June, July, August, September, October, November and December adapted for use' in any year, an individual card for each of the months of January and February adapted for use in leap years only and an individual card for each of the months of January and February adapted for use in common years only, each of said fourteen cards being marked at thirteen equally spaced columns with days of the month indicia, the interval between successive positions of said columns being the same as the interval between the successive positions of the days of the week indicia on the templates, the size and position of the window on each template being'v such that each template when placed in a standard manner above any one of said cards hides six of the thirteen columns of day numbers and exposes seven consecutive columns thereof, the po-A sition of the window from template to template in the series being different by the constant interval between columns, so that each of the seven templates exposes a different combination of seven columns, but the same Vcombination on4 every card.

JOHN Q. STEWART. 

